PROGRAMS AND PLANS--Transport Modeling System Announced In Reply Refer To: January 5, 1990 WGS-Mail Stop 415 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 90.05 SUBJECT: PROGRAMS AND PLANS--Transport Modeling System Announced The Offices of Surface Water and Water Quality have been attempting to develop a flow and transport modeling system for the past several years. The main elements of this system are two flow models and one transport model. One flow model (BRANCH) and the transport model (BLTM) have been previously documented and rather extensively used in Water Resources Division (WRD). The purpose of this memorandum is to announce the publication of the third model via "Users Manual for an Open-Channel Streamflow Model based on the Diffusion Analogy" (DAFLOW) by Harvey E. Jobson as Water-Resources Investigations Report 89-4133. These three models offer a flexible and robust transport modeling system. The DAFLOW model is designed to predict discharge and flow velocity using a minimum of field data for a system of one- dimensional open channels. The model requires relatively few data (it does not require cross sections for example), is very easy to apply and understand (the code contains only 772 lines), and is most accurate for upland streams with steep slopes. The DAFLOW model is a version of the old CONROUT model that was successful in many WRD applications. The required data are bed slope, an average top width at one flow, and either a Manning's n or the wave speed for one flow. The model is menu driven and incorpo- rates the hydraulic geometry coefficients developed in the field of geomorphology to enhance its predictive capability. The BRANCH model has been in use for some time, however, it suffers a few limitations. It is data intensive and requires a fairly high level of skill to use. It also tends to be unstable for upland streams where the frictional slope is approximately equal to the bed slope. The BRANCH model works well, however, for low gradient streams and estuaries. Together the BRANCH and the DAFLOW models, therefore, complement each other very well in covering the entire range of flow situations encountered by WRD. Either BRANCH or DAFLOW can be used to drive a transport model such as the BLTM. The BLTM model can be used to route any number of dissolved constituents through a system of one dimensional channels. The kinetics of the constituents are defined in a subroutine called FINK. FINK subroutines are available for temperature, the nitrogen cycle, the QUAL II kinetics, bass-egg development, and fine sediment. Attached is a list of past and potential transport projects that have used one or more of the models. Copies of DAFLOW and or BLTM model documentation and codes (for either the prime or a PC) can be obtained from the Office of Surface Water. Copies of the BRANCH flow model are available through David Thompson at the Office of Surface Water's Flow and Transport Modeling group at Stennis Space Center. Charles W. Boning Chief, Office of Surface Water Attachment WRD DISTRIBUTION: A, B, S, FO, PO